Radiotelegraph system



July 31, 1923. 1,463,391

E. c. HANSON ET AL RADIO TELEGRAPH SYSTEM Filed Feb. 11, 1920 2 Sheets-Sheet 1 July 31, 1923.

E. c. HANSON ET AL RADIO TELEGRAPH SYSTEM Filed Feb. 11. 1920 2 Sheets-Sheet 2 EARL o. HANSON AND WENDELL L. CARLSON, OE WASHINGTON,- DISTRICT OF COLUMBIA.

RADIOTELEGRAPH SYSTEM.

' Application filed February 11, 1920. Serial No. 357,919. I

T all whom it may concern:

Be it known that we,-EAnL C. HANSON and WENDELL L. CARLSON, citizens of the United States, residing at Washington, Dis-.

trict of Columbia, have invented certain new and useful Improvements in Radiotelegraph Systems, of which the following is a specification.

Our invention relates to the reception of wireless signals and more particularly to those systems operating on the undamped wave principle.

Heretofore, in order to actuate a signal responsive device it has been generally necessary to convert the received radio frequency energy directly into an audible frequency.

The object of our invention is to provide an arrangement .for receiving undamped radio wave signals without first converting the radio frequency energy into an audible frequency as is usually necessary 1n the case of the heterodyne, or other systems.

Another object of this invention is to provide an electric circuit for first recording radio signals .and subsequently reproducing the recorded signals. I

A further object of the present invention is to provide a circuit which will respond efficiently to sustained radio fre uencies but which will not respond efiicient y to audio frequencies and strays.

The novel features which we believe to be characteristic of our invention are set forth with particularity in the appended claims.

' The invention itself, however, both as to particular embodiments thereof and its mode of operation, will be best understood by reference to the following description taken in connection with the accompanying drawings, wherein- Figure 1 shows diagrammatically a telegraphone associated with an audio frequency oscillating vacuum tube circuit. The moving steel wire of the telegraphone is magnetized in accordance with the audio frequency of the oscillatory circuit.

Figure 2 shows the recording circuit associated with an antenna circuit through a vacuum tube detector and a thermionic vacuum tube amplifier. Figure 2 also shows the reproducing circuit comprising the reproducer of the telegraphone, the thermionic vacuum tube amplifier, and signal responsive device.

Referring particularl to the diagram shown in Figure 1, re erence character 1 represents a thermionic vacuum tube associated with coupling coils 2 and 3 forming an oscillating circuit. The telegraphone 4 as shown comprises the recording magnets 5 and the moving steel wire 5 operated by means of the reel mechanism indicated at 5 The telegraphone is a well known apparatus and need not be described herein.

In Figure 2, reference character 6 represents an antenna circuit tuned to the incoming radio frequency signal. Associated with the antenna circuit 6 is a resonant secondary circuit 7 and 7 definitely designed for the frequency of the received signal. Connected to this resonant circuit 7 and 7 is a multistage high power amplifier comprising the thermionic vacuum tubes 8 and 10 and tuned radio frequency transformers 9 and 11.

Interposed between the amplifier circuit and recording telegraphone 4. is a thermionic vacuum tube detector 12. The usual grid condenser 20 and the resistance leak 21 are 5 are connected in the plate circuit of the detector tube 12. The fixed condenser 13 is shunted across the windings 5. The repro-' ducing windings 14 of the telegraphone 4 are connected to the input of an audio frequency amplifier consisting of the audio frequencytransformers 15 and 17 and the thermionic vacuum tubes 16 and 18. A signal responsive device 19 is connected to the output of the vacuum tube amplifier.

The operation of the system is as follows:

First consider that the tuned circuits 6 and 7- of the receiving apparatus are adjusted to receive sustained radio frequencies, as for example 10,000 meters (30,000 cyles). The radio frequency is amplified through the thermionic vacuum tubes 8 and 10. The radio frequency impressed on the grid of the rectifier tube 12 produces a series of rectified half cycles in the plate circuit. In

tier the direct current in the plate circuit may either increase or decrease when an alternating potential is impressed upon the grid circuit, depending on the potential at which the grid is operated. For instance, if the grid is operated at a negative potential with respect to the filament tht positive half of the impressed wave-will detzrease the resistance of the plate circuit to a greater extent than the negative half. of the wave will increase the resistance of the plate circuit. The result of these two actions is to decrease the resistance from plate to filament, thereby causing an increase in the direct current of the plate circuit.

It the grid is operated at a positive potential with respect to the filament the direct current in the plate circuit will decrease when an alternating potential is impressed on the grid. The grid of the tube 12 is worked at positive potential with re spect to the filament, and the condenser 20 and grid leak 21 are placed in the grid circuit of the tube 12 merely to give a more efiicient rectification of the incoming signal. The capacity 13 is so proportioned in relation to the inductance 5 as to provide a very low impedance path to audio and radio frequencies.

In fact the constants of the plate circuit may be adjusted to a natural period as low as thirty cycles per second. This frequency will be determined by the speed at which the signals are transmitted. The circuit must respond to a frequency corresponding to the time required to transmit a dot in the ordinary radio telegraph signal system.

In order to record the received inaudible signals we resort to the novel method of initially magnetically saturating the moving steel wire of the telegraphone with an audio frequency of, for example, 500 cycles, by means of the oscillating vacuum tube circuit shown in Figure l. I

In recording the signals on the moving wire of the telegraphone the direct current in the plate circuit of the tube 12 is utilized to magnetize the recording windings 5. When the recording wire passes the pole pieces of the windings 5 the audio frequency magnetic impressions previously recorded on the wire are erased in accordance with the strength of the magnetic field produced by the direct current in the windings 5.- lit is seen that the erasing process on the teleg raphone wire will diminish with the crop in plate current, and therefore will decrease in strength in accordance with the incoming signals. This process has the effect of erasing the signals from the record during the intervals between the signal characters and retaining the record in accordance with the signal characters.

Tn the reproduction process the recording wire passes the windings it and induces an nceasei audio frequency current therein in accordance with the audio frequency impressions not erased in the recording process. This audio frequency signal is amplified by the thermionic vacuum tube amplifier and operates any suitable signal responsive device 19.

Having thus described our invention what of receiving radio signals, consisting in initially magnetically saturating a telegraphone wire continuously at an audible fre quency, receiving signal energy, amplifying and rectifying said energy, subjecting said record to the action of said amplified and rectified energy, and causing the resulting I signal record to actuate an amplifier adapted to intensify the signal energy to a point suiiicient to operate a responsive device.

3. In a system for receiving radio telegraph signals, the method which consists in energizing the record wire of a telegraph'one at an audio frequency causing said record wire to be continuously stored in bulk after energization, unwinding said wire from said stored condition, and causing the energy to be erased magnetically during the periods of space between the received signal characters and reproducing the signals at the aforesaid 'aud'io frequency, amplifying said signals and causing them to actuate a responsive device;

4:. In a system for the reception of radio signals the method which consists in receiving the signal energy and directly amplifying same at radio frequency, rectifying the energy to obtain a direct current variation in a circuit in accordance with signals, superimposing these variations magnetically upon a moving record of a telegraphone pre viously energized at an audio frequency, and reproducing the record remaining on the telegraphone wire for translation into readable signals.

5. Tn a system. for the reception of radio signals, the method consisting in receiving signal energy and converting it into direct current pulsations and causing it to magnetically efface a continuous audio frequency record on a telegraphone wire in such manner as to annul the energy on said wire during the period of space between said sig nal characters.

. 6. In a radio telegraph system, the method ten llO

lllti tervals between the signal characters, and means for receiving radio signals and causamplifying the signal energy retained on the ing a direct current variation in a circuit telegraphone record to a degree sufiicient-to and means whereby said direct current erases actuate a responsive device. the energy from said wire in the intervals 5 7. In a radio telegraph system a telegrabetween the received signal characters and 15 phone having two reels and in which the means for reproducing the signal record record wire is unwound from one reel and stored on said wire for translation.

stored in bulk upon the other, means for energizing said record wire during its pas- EARL C. HANSON.

10 sage from one to the other of said reels, WENDELL L. GARLSON. 

